Imaging and electron energy-loss spectroscopy using single nanosecond electron pulses

Nanosecond electron pulses in the analytical electron microscopy of a fast irreversible chemical reaction

“…Time-resolved TEM experiments are carried out in an ultrafast TEM 12,22 where nanosecond electron pulses are used for imaging, electron diffraction, and EELS (see Methods Section). The experimental setup of the single-shot experiment has been described in detail previously 12 . A TEM with 200 kV acceleration voltage, equipped with an EEL spectrometer and a photoemitter (1 mm Ta disc), was used.…”

“…It has to be taken into account that only a very small fraction of the pulse energy is absorbed and heats the sample. Since an irreversible reaction is studied, the procedure had to be carried out in the single-shot approach 8,9,12 where only one intense electron pulse is used. By setting adjustable delays between the sample laser heating pulse and the electron probe pulse generated on the photocathode by a 7 ns UV laser pulse (213 nm) from the second nanosecond laser, we studied the evolution of the reduction and transformation of the sample.…”

“…By setting adjustable delays between the sample laser heating pulse and the electron probe pulse generated on the photocathode by a 7 ns UV laser pulse (213 nm) from the second nanosecond laser, we studied the evolution of the reduction and transformation of the sample. Due to the unavoidable electron-electron interaction within the pulse, this entails several restrictions in spatial and energy resolution of the electron-optical system 12 in comparison to standard TEM with continuous electron beams.…”

“…Since then, chemical information about the elemental distribution during fast irreversible transformations has yet to be demonstrated in dynamic TEM studies. This problem has recently been solved by using a modified photo-gun and TEM electron optical configuration to filter the electron pulses and improve their energy resolution while providing for high-collection efficiency in the spectrometer 12 .…”

Atomic-scale imaging of ultrafast materials dynamics

“…20,23 In their article, 30 Pomarico et al describe the exciting developments occurring with fs-EELS, including ultrafast valence and core-loss dynamics, the direct imaging of coherent, low-energy plasmonic resonances and decay dynamics at surfaces and interfaces, and the recent development of nanosecond, single-shot EELS. 31 In conventional core-loss EELS experiments, energy losses due to excitation/ionization of core-level electrons can be used to identify the local composition and oxidation states of elements. Additionally, the fine structure near the main spectral features contains a wealth of information pertaining to, for example, local bonding conditions.…”